How Do You Teach Reasonableness?!?

So as I laid in bed a few nights ago because I couldn't turn my brain off, I got thinking about the batch of marking that I had done earlier in the day.  It was a math formative assessment that followed a weeks worth of lessons on proportional reasoning and consequently the reasonableness of our answers.  What kept coming to my mind was "how do I go back and teach reasonableness again?" because it seemed every answer I read I wonder who would have submitted this if they had only re-read their answer to check if it made sense.  We've had a new vision in math these past few years in going to more of a problem solving approach (which I love by the way), so I try to keep an open mind when reading the work of my students.  I preach on a daily basis that we all take different routes to school in the morning and all end up at the same place, so we can do the same thing with a math problem.  However, I often make my students laugh when I ask if they think it's reasonable that I head to Montreal first before coming to school just to prove my point that sometimes our answers are not the best avenues to take.  But this isn't sticking with them...so now what?!

As a part of our School Learning Team it was one of our focuses this year to get students to re-read their work before submitting it (regardless of the subject area) and I seem to be failing miserably with this focus.  I'm at a loss as to how to get this point across.  I've thought of giving them the whole "can't hand it in until you've read it over" or "you must take a minimum of 10 minutes to solve the problem before handing it in", but it isn't teaching the kids what to look for.  They are solving the problem to the best of their ability and if they knew the answer was not right then they wouldn't have written it in the first place.  I always consolidate answers to problems that have a high rate of inaccuracy and when I do the light clicks, but it doesn't always stay on for the next time.  So my big question is "now what?".  Please leave me any comments or suggestions here or on my twitter at @stephwardranger

Have a good week!

Stephanie :)